X-ray techniques are used in a wide range of apparatus, such as metrology applications in semiconductor manufacturing processes. Examples of prior art techniques are provided below.
U.S. Pat. No. 6,282,263, to Arndt, et al., whose disclosure is incorporated herein by reference, describes an X-ray generator which produces an X-ray source having a focal spot or line of very small dimensions and which is capable of producing a high intensity X-ray beam at a relatively small point of application using a low operating power.
European Patent 2,050,100, to Boulee, et al., whose disclosure is incorporated herein by reference, describes a system for delivering an X-ray beam, comprising a source block that emits a source X-ray beam and conditioning means for conditioning the source beam sent towards a specimen. The system includes stabilization means designed to thermally stabilize a region of the system lying downstream of the source block, in order to limit heat transfer towards the conditioning means for the purpose of preventing thermal perturbations in the conditioning means.
U.S. Pat. No. 6,935,778, to Bievenue, et al., whose disclosure is incorporated herein by reference, describes methods and devices for aligning and determining the focusing characteristics of X-ray Optics. The methods and devices are stated to simplify the process of aligning an X-ray optic device to an X-ray source or for measuring a focusing characteristic, for example, the focal length or beam shape, of an X-ray optic.
U.S. Pat. No. 7,104,690, to Radley, et al., whose disclosure is incorporated herein by reference, describes a diagnostic technique for an X-ray source. A system monitors existing conditions (e.g., tube current) in the source to track degradation of certain components to anticipate failure. Storage of past characteristics and reference characteristics is also provided for predicting failure and other operating conditions of the source. Communication techniques are provided for the monitoring and warning functions.
U.S. Pat. No. 7,257,193, to Radley, et al., whose disclosure is incorporated herein by reference, describes an X-ray source assembly having enhanced output stability using tube power adjustments and remote calibration. A control system is provided for maintaining intensity of the output X-rays dynamically during operation of the X-ray source assembly, notwithstanding a change in at least one operating condition of the X-ray source assembly, by changing the power level supplied to the assembly. The control system may include at least one actuator for effecting the change in the power level supplied to the assembly, by, e.g., controlling a power supply associated with the assembly. The control system may also change the temperature and/or the position of the anode to maintain the output intensity.
U.S. Pat. No. 8,515,012, to Koppisetty, et al., whose disclosure is incorporated herein by reference, describes an X-ray tube with high speed beam steering electromagnets. The X-ray tube includes an electron beam source, a target configured to generate X-rays when impacted by an electron beam from the electron beam source, and a steering magnet assembly having a plurality of ferrite cores and a plurality of litz wire coils wound on the ferrite cores.